A Double-Prism Attenuator For Millimeter Waves (Correspondence)

A double-prism attenuator, similar to the one built by Garnham for use at 35 Gc, was built in the laboratory for use at 100 Gc and above. This attenuator utilizes the well-known fact that a wave which is incident on the interface between two dielectrics at an angle greater than the critical angle is totally reflected. If the wave is in a medium of index of refraction n and the other medium is free space the critical angle is θ_c = sin^-1 1/n.